MARION -- Mayor Robert "Bob" Butler -- a man many have credited with Marion's vast commercial growth and a man who made the city a destination for investors for several decades -- will officially step down from his position of 55 years on Jan. 31.

Butler is one of the longest-serving mayors in United States history, having first taken office in 1963, more than two generations ago.

The 90-year-old offered his explanation of why he is retiring a little more than 14 months before his current mayoral term ends in April 2019.

"My hearing has deteriorated to the point that I can't adequately carry on my duties as I believe I should," Butler said. "I have been trying to come up with the right time to make this announcement ever since my hearing began to get worse. I was planning to send out a press release on Monday."

Butler said he will take vacation time the entire month of December, then return to his job for one final month after the New Year's holiday.

"I haven't had a vacation in several years, so I thought this would be a good time to take one," he said. "When I come back in January, I have some loose ends I want to tie up before I am done."

By state statute, the city's finance commissioner -- Anthony Rinella -- becomes the mayor pro tem. He will be sworn into office Feb. 1 and will complete the mayor's term of office. He earlier announced his intention to run for mayor in 2019.

Commissioner Angelo Hightower has also announced his candidacy for mayor of Marion.

The Marion council has 60 days to appoint a replacement for Rinella as city commissioner.

"Anthony is aware of my plan to retire, but we have not discussed the transition yet," Butler said. "I don't see any complications. I wish him only the best."

Rinella said it is "quite humbling" to realize that he will be replacing a man who has been at his job for so long.

"I'm sure there will be those who say that the mayor is doing this to put me in a better position for election in 2019, but anyone who thinks that doesn't know Bob Butler," Rinella said. "There's no quit in him. If it weren't for his health, he would absolutely finish his term of office. He wouldn't be stepping down if not for a compelling reason, and that reason is his hearing."

Rinella, 62, is a lifelong resident of Marion. He served the city's fire department for 32 years, including 6½ years as chief.

"I decided at the last election in 2015 that I would run for mayor in 2019 if Mayor Butler was not going to run again, so this is something I have been thinking about for a while now," he said. "I'd like to think people are pretty comfortable with me. And I'd like to think that they know they can trust me. I think I'm well suited for the job."

Butler said there is no secret to his success or longevity in office.

"I know I am going to miss working with people and trying to be of benefit to this community," he said.